assert_string_contains: Assert string contains a regex pattern

In assertions: Simple Assertions for Beautiful and Customisable Error Messages

Assert string contains a regex pattern

Description

Assert a string matches a regex pattern.

Usage

assert_string_contains(
  x,
  pattern,
  ignore.case = FALSE,
  perl = FALSE,
  fixed = FALSE,
  useBytes = FALSE,
  msg = NULL,
  call = rlang::caller_env(),
  arg_name = NULL
)

Arguments

x	An object to check
pattern	A regular expression pattern (string)
ignore.case, perl, fixed, useBytes	Logical flags passed to grepl()
msg	A character string containing the error message to display if x does not match pattern
call	Only relevant when pooling assertions into multi-assertion helper functions. See cli_abort for details.
arg_name	Advanced use only. Name of the argument passed (default: NULL, will automatically extract arg_name).

Value

invisible(TRUE) if x matches pattern, otherwise aborts with the error message specified by msg

Examples

try({
assert_string_contains("abc", "^a") # Passes
assert_string_contains("abc", "^b") # Throws default error
assert_string_contains("abc", "^b", msg = "Custom error message") # Throws custom error
})

assertions documentation built on Feb. 13, 2026, 5:06 p.m.